1. Field of the Invention
This invention relates to an exposure apparatus, an exposure method, and a device manufacturing method.
2. Description of Related Art
There exist exposure apparatuses which employ catadioptric type projection optical systems using a concave mirror, such as that described for example in Japanese Unexamined Patent Application, Publication No. H06-132191. In this type of exposure apparatus, it is known that when an area shifted from the optical axis of the projection optical system is used as the exposure area, if the projection magnification is changed, the center of the projected image is shifted (image shift). Japanese Unexamined Patent Application, Publication No. 2004-145269 discloses technology to insert an optical element for correction into the optical path, in order to correct image shift.
In technology of the prior art such as that described above, when an optical element to correct image shift is provided and is inclined to correct image shift, there is the possibility of fluctuation of other aberrations. Further, when the projection magnification is changed, the baseline value, which is the distance between the reticle center and the alignment optical system, fluctuates due to image shift, and so processing to measure the baseline value is again performed. If the baseline value is measured each time the projection magnification is changed, throughput falls sharply.
A purpose of some aspects of the invention is to provide an exposure apparatus, an exposure method, and a device manufacturing method which enable high-precision exposure processing.